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module EZGUI {
    export var Easing = {

        Linear: {

            None: function (k) {

                return k;

            }

        },

        Quadratic: {

            In: function (k) {

                return k * k;

            },

            Out: function (k) {

                return k * (2 - k);

            },

            InOut: function (k) {

                if ((k *= 2) < 1) return 0.5 * k * k;
                return - 0.5 * (--k * (k - 2) - 1);

            }

        },

        Cubic: {

            In: function (k) {

                return k * k * k;

            },

            Out: function (k) {

                return --k * k * k + 1;

            },

            InOut: function (k) {

                if ((k *= 2) < 1) return 0.5 * k * k * k;
                return 0.5 * ((k -= 2) * k * k + 2);

            }

        },

        Quartic: {

            In: function (k) {

                return k * k * k * k;

            },

            Out: function (k) {

                return 1 - (--k * k * k * k);

            },

            InOut: function (k) {

                if ((k *= 2) < 1) return 0.5 * k * k * k * k;
                return - 0.5 * ((k -= 2) * k * k * k - 2);

            }

        },

        Quintic: {

            In: function (k) {

                return k * k * k * k * k;

            },

            Out: function (k) {

                return --k * k * k * k * k + 1;

            },

            InOut: function (k) {

                if ((k *= 2) < 1) return 0.5 * k * k * k * k * k;
                return 0.5 * ((k -= 2) * k * k * k * k + 2);

            }

        },

        Sinusoidal: {

            In: function (k) {

                return 1 - Math.cos(k * Math.PI / 2);

            },

            Out: function (k) {

                return Math.sin(k * Math.PI / 2);

            },

            InOut: function (k) {

                return 0.5 * (1 - Math.cos(Math.PI * k));

            }

        },

        Exponential: {

            In: function (k) {

                return k === 0 ? 0 : Math.pow(1024, k - 1);

            },

            Out: function (k) {

                return k === 1 ? 1 : 1 - Math.pow(2, - 10 * k);

            },

            InOut: function (k) {

                if (k === 0) return 0;
                if (k === 1) return 1;
                if ((k *= 2) < 1) return 0.5 * Math.pow(1024, k - 1);
                return 0.5 * (- Math.pow(2, - 10 * (k - 1)) + 2);

            }

        },

        Circular: {

            In: function (k) {

                return 1 - Math.sqrt(1 - k * k);

            },

            Out: function (k) {

                return Math.sqrt(1 - (--k * k));

            },

            InOut: function (k) {

                if ((k *= 2) < 1) return - 0.5 * (Math.sqrt(1 - k * k) - 1);
                return 0.5 * (Math.sqrt(1 - (k -= 2) * k) + 1);

            }

        },

        Elastic: {

            In: function (k) {

                var s, a = 0.1, p = 0.4;
                if (k === 0) return 0;
                if (k === 1) return 1;
                if (!a || a < 1) { a = 1; s = p / 4; }
                else s = p * Math.asin(1 / a) / (2 * Math.PI);
                return - (a * Math.pow(2, 10 * (k -= 1)) * Math.sin((k - s) * (2 * Math.PI) / p));

            },

            Out: function (k) {

                var s, a = 0.1, p = 0.4;
                if (k === 0) return 0;
                if (k === 1) return 1;
                if (!a || a < 1) { a = 1; s = p / 4; }
                else s = p * Math.asin(1 / a) / (2 * Math.PI);
                return (a * Math.pow(2, - 10 * k) * Math.sin((k - s) * (2 * Math.PI) / p) + 1);

            },

            InOut: function (k) {

                var s, a = 0.1, p = 0.4;
                if (k === 0) return 0;
                if (k === 1) return 1;
                if (!a || a < 1) { a = 1; s = p / 4; }
                else s = p * Math.asin(1 / a) / (2 * Math.PI);
                if ((k *= 2) < 1) return - 0.5 * (a * Math.pow(2, 10 * (k -= 1)) * Math.sin((k - s) * (2 * Math.PI) / p));
                return a * Math.pow(2, -10 * (k -= 1)) * Math.sin((k - s) * (2 * Math.PI) / p) * 0.5 + 1;

            }

        },

        Back: {

            In: function (k) {

                var s = 1.70158;
                return k * k * ((s + 1) * k - s);

            },

            Out: function (k) {

                var s = 1.70158;
                return --k * k * ((s + 1) * k + s) + 1;

            },

            InOut: function (k) {

                var s = 1.70158 * 1.525;
                if ((k *= 2) < 1) return 0.5 * (k * k * ((s + 1) * k - s));
                return 0.5 * ((k -= 2) * k * ((s + 1) * k + s) + 2);

            }

        },

        Bounce: {

            In: function (k) {
                
                return 1 - EZGUI.Easing.Bounce.Out(1 - k);

            },

            Out: function (k) {

                if (k < (1 / 2.75)) {

                    return 7.5625 * k * k;

                } else if (k < (2 / 2.75)) {

                    return 7.5625 * (k -= (1.5 / 2.75)) * k + 0.75;

                } else if (k < (2.5 / 2.75)) {

                    return 7.5625 * (k -= (2.25 / 2.75)) * k + 0.9375;

                } else {

                    return 7.5625 * (k -= (2.625 / 2.75)) * k + 0.984375;

                }

            },

            InOut: function (k) {

                if (k < 0.5) return EZGUI.Easing.Bounce.In(k * 2) * 0.5;
                return EZGUI.Easing.Bounce.Out(k * 2 - 1) * 0.5 + 0.5;

            }

        }

    }
}
